In the refining of metals, e.g. the oxygen refining of steel, it has been a growing practice to inject air or oxygen below the surface of the melt or to train a jet of air or oxygen onto the melt surface, with or without entrainment of refining (e.g., deoxidizing), alloying or other reactive materials in the gas stream.
The lances may be thrust below the surface of the slag layer overlying the metal bath or may merely penetrate the slag layer to blow gas into the melt from the top.
In all of these cases, a significant problem has been recognized in the art with respect to encrustation or coating of the lance with slag and metal, either by spattering from the surface of the bath or by direct contact of the lance with the bath, the encrustations solidifying upon the lance in the form of a layer which greatly increases the weight of the lance and the difficulty of its manipulation.
Attempts have been made to remove this layer manually by torches and/or chisels and even automatically by using a scraper against which the lance is drawn by the means enabling its manipulation and return to its repose state out of the melt, ladle, converter or furnace in which the refining takes place.
Whether the technique used in manual or automatic, there are certain problems which have arisen in connection with the attempts to remove the encrusting layers from the lance. Especially when the layer contains metal it is extremely hard and frequently is relatively thick so that the force which must be used is considerable and may endanger the lance or the means for manipulating same. Other techniques involve this disadvantage and also require very long times for removal of the crusts while other techniques, including those requiring the use of torches, are time consuming and possible detrimental to the lance itself. Until now, therefore, a completely satisfactory system for removing slag and metal deposits on metallurgical lances has not been developed.